Origin of the word is thus far known to be Polwarth (Edinburgh), where a youth gang of 3 members (!!!) brought the word to its current state of fame. The word itself is an abbreviation of a posh wank - masturbation with the use of a condom to avoid major cum spillage and, according to one member of the gang (Heeaada), self fertilisation. The word is believed to have german influences. The word is mostly used by its self, often bawled out without direct relation to the conversation. The provocations for shouting "poschyen" are essentially unnumnbered. Example are a cry of protest but more likely it is used to convey sexual desire towards another human being, animal or object.
"That bird on the balcony is sooo tidy!"